PHILADELPHIA – The Philadelphia Eagles hid their flaws and overcame glaring weaknesses for three-quarters of the season.

Then came December.

Three straight losses, including a crushing 27-24 defeat to Washington (4-11) on Saturday, cost the Eagles (9-6) a spot in the playoffs. A Dallas victory over Indianapolis on Sunday afternoon sealed Philadelphia’s fate.

No one could’ve predicted this collapse after Philadelphia whipped the Cowboys 33-10 on the road on Thanksgiving to take control of the NFC East.

But the Eagles followed that up with home losses to Seattle and Dallas before falling flat against the Redskins, who snapped a six-game losing streak with the victory.

“It’s very frustrating to us to control our destiny when we are 9-3 and to have this happen,” said tight end Zach Ertz, who set a franchise record with 15 catches against Washington. “We’re very disappointed. Ultimately, it falls on the players. We didn’t execute the game, either of the three games. It’s very disheartening.”

The Eagles would win the division if they beat the Giants next week and the Cowboys finish with losses to the Colts and at Washington. They don’t have a chance at a wild-card berth.

A turnover-prone offense and defense that allows too many big plays were the downfall for this team. The Eagles found ways to hide their mistakes and win games for most of the season, but couldn’t do it any longer. They were helped early in the season by 10 touchdowns from their special teams and defense.

But once they stopped getting those bonus scores, they struggled. Meanwhile, the offense kept turning the ball over.

Mark Sanchez threw for a career-high 374 yards and had a franchise-record 37 completions against the Redskins, but his interception in the final minutes paved the way for Washington’s win.

Sanchez has 14 turnovers in eight games since replacing Nick Foles after he broke his collarbone. Foles had 13 turnovers.

“You have to win games,” Sanchez said. “The head coach and the quarterback, we are the only ones who keep a record, so it goes with the territory of this position. There have been three really tough games and this one came down to the wire and we came up a little short.”

Penalties hurt the Eagles during the three-game losing streak, especially ones committed by the defense. The defense had three penalties against the Redskins on the third down that kept drives going and resulted in 17 points.

“You aren’t going to win a football game that way,” coach Chip Kelly said. “We left them on the field too long.”

The secondary also allowed several big plays, including a pair of 50-yard receptions by DeSean Jackson on Bradley Fletcher. Last week, Dez Bryant caught three touchdown passes against Fletcher. Cary Williams switched over to cover Bryant after the damage. Fletcher was finally benched in base defense situations after Jackson caught four passes for 126 yards against him.

Several of those passing plays came when defensive coordinator Billy Davis allowed Fletcher to cover his man one-on-one with no safety help. Nate Allen intercepted Robert Griffin III on one deep pass to Jackson when the Eagles double-covered their former teammate.

“I make plans based on what I see and make decisions on what I see,” Davis said. “I don’t regret one minute of it.”

Then there were a pair of missed field goals by rookie Cody Parkey, who was 29 for 31 entering the game.